Split a string on newlines in C++

This post will discuss how to split a string on newlines in C++.

1. Using `std::getline`

A simple solution to split a string on newlines is using the std::getline function. It can be used to extract tokens from the input stream delimited by the newline, as shown below:

#include <iostream>

#include <string>

#include <vector>

#include <regex>

std::vector<std::string> splitString(const std::string& str)

{

std::vector<std::string> tokens;

std::stringstream ss(str);

std::string token;

while (std::getline(ss, token, '\n')) {

tokens.push_back(token);

}

return tokens;

}

int main()

{

std::string str = "C\nC++\nJava";

std::vector<std::string> tokens = splitString(str);

for (auto const &token: tokens) {

std::cout << token << std::endl;

}

return 0;

}

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Output:

C
C++
Java

2. Using `string::find`

The std::string::find member function searches a string for the specified character, starting from the specified position. It returns the first occurrence of the specified character and string::npos if it is not found. It can be used as follows to split a string on newlines:

#include <iostream>

#include <string>

#include <vector>

std::vector<std::string> splitString(const std::string& str)

{

std::vector<std::string> tokens;

std::string::size_type pos = 0;

std::string::size_type prev = 0;

while ((pos = str.find('\n', prev)) != std::string::npos) {

tokens.push_back(str.substr(prev, pos - prev));

prev = pos + 1;

}

tokens.push_back(str.substr(prev));

return tokens;

}

int main()

{

std::string str = "C\nC++\nJava";

std::vector<std::string> tokens = splitString(str);

for (auto const &token: tokens) {

std::cout << token << std::endl;

}

return 0;

}

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Output:

C
C++
Java

3. Using Boost

Finally, we can use the boost::algorithm::split_regex algorithm offered by the boost library to split the input sequence into tokens, separated by separators. This function is equivalent to C strtok and is available in the header <boost/algorithm/string/regex.hpp>.

#include <iostream>

#include <string>

#include <vector>

#include <regex>

#include <boost/regex.hpp>

#include <boost/algorithm/string/regex.hpp>

std::vector<std::string> splitString(const std::string& str)

{

std::vector<std::string> tokens;

split_regex(tokens, str, boost::regex("(\r\n)+"));

return tokens;

}

int main()

{

std::string str = "C\nC++\nJava";

std::vector<std::string> tokens = splitString(str);

for (auto const &token: tokens) {

std::cout << token << std::endl;

}

return 0;

}

Download Code

Output:

C
C++
Java

That’s all about splitting a string on newlines in C++.

Split a string on newlines in C++

1. Using std::getline

2. Using string::find

3. Using Boost

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1. Using `std::getline`

2. Using `string::find`